INTRODUCTION
Bronchopulmonary dysplasia (BPD) or neonatal chronic lung disease (CLD) represents a common and complex cardiorespiratory morbidity that affects preterm infants. Despite advances in care, the prevalence of BPD has remained constant due to increased survival of extremely low gestational age newborns (ELGAN).1 It is estimated that 45% of ELGANs are diagnosed with BPD. Pathologically, BPD is characterized by abnormal lung development and lung injury with varying degrees of disrupted alveolarization, vascular remodeling, inflammatory cell proliferation and pulmonary edema. Lung morbidity associated with BPD increases the risks for prolonged oxygen and respiratory support requirements, pulmonary hypertension, impaired growth, and poor neurodevelopmental outcomes. As such, the prevalence of BPD represents an essential indicator for benchmarking the quality of neonatal care.2
Management of BPD includes strategies to avoid invasive mechanical ventilation together with aggressive pharmacologic and nutritional interventions. While limiting mechanical ventilation and enhancing caloric intake have been shown to improve outcomes in BPD patients, the long-term benefits of medications such as steroids and diuretics for BPD remain uncertain. In ELGANs with BPD who require increased intravenous or enteral intake to ensure metabolic requirements, diuretics are used very commonly to improve pulmonary function despite limited data regarding their-long term efficacy and safety.3-5 In the short term, they improve pulmonary function by decreasing interstitial pulmonary fluid, which can contribute to increased lung compliance, decreased airway resistance, and subsequently decreased respiratory support.6-10 Despite these improvements in pulmonary mechanics, a series of 2011 Cochrane reviews did not demonstrate long-term benefits, so routine diuretic use for infants with active or developing chronic lung disease was not recommended.11,12 In contrast, a more recent retrospective study of over 37,000 premature infants, approximately half of whom had received furosemide, found that for every 10% increase in furosemide exposure-days, there was a 4.6% decrease in the incidence of BPD.3
Recent advances in lung ultrasound (LUS) diagnosis of neonatal diseases offer more sensitive detection of pulmonary edema regardless of its cause.13 Excess water outside of pulmonary blood vessels can be quantified using LUS by the finding of “B-lines”. In animal studies, the number of B-lines has been directly correlated with the severity of pulmonary edema.14 Studies in neonates with congenital heart disease with pulmonary overflow have found LUS to be a useful tool to assess pulmonary edema.15 Similar findings have been reported in infants with pulmonary edema caused by patent ductus arteriosus.16
Our primary objective was to quantify and compare pulmonary edema before and after initiation of diuretic therapy for infants with evolving CLD using LUS. The secondary objective was to assess changes in respiratory support parameters during the week after initiation of diuretics.